java 反射 constructors的问题，真心需要解决

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解决时间 2021-01-25 15:17

已解决

2021-01-25 10:12

java.lang.IllegalArgumentException: wrong number of arguments

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)

at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

at test._01reflect.Reflect.main(Reflect.java:17)

源代码是：

public class Student {

private int age;

private String name;

public Student() {

super();

}

public Student(String name) {

super();

this.name = name;

}

public Student(int age) {

super();

this.age = age;

}

public Student(int age, String name) {

super();

this.age = age;

this.name = name;

}

}

main方法：

public static void main(String[] args) {

try {

Class cls = Class.forName("test._01reflect.Student");

Student stu = null;

//获取构造函数

Constructor>[] con = cls.getConstructors();

stu = (Student)con[0].newInstance();//第17行

stu = (Student)con[1].newInstance(25);

stu = (Student)con[2].newInstance("maosheng");

stu = (Student)con[3].newInstance(25,"maosheng");

各位大神，这是哪里的错误啊，小弟实在解决不了

最佳答案

2021-01-25 11:25

con 里面的顺序是与student类中的构造方法的顺序一致

所以将

stu = (Student)con[1].newInstance(25);

stu = (Student)con[2].newInstance("maosheng");

调换一下位置就可以了

stu = (Student)con[1].newInstance("maosheng");

stu = (Student)con[2].newInstance(25);

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